In known forms of lever-operated grease guns as disclosed for example, in the U.S. Pat. Nos. 2,923,443, 2,941,854, and 3,780,830 it is a prevalent practice to thread both ends of a grease-containing cylinder for screwing thereonto the head end cap of a dispensing head assembly and the rear end cap of spring-biased plunger and rod assembly of which the rod is operative to retract the plunger in the cylinder for filling the same with grease in bulk or cartridge form and of which the plunger is effective to feed grease in the cylinder to the lever-operated pump of the dispensing head assembly.